Authorities say a parent has barricaded himself in a Southern California elementary school classroom with at least one other person.Riverside police Officer Ryan Railsback tells KCAL-TV that the incident at Castle View Elementary School was reported shortly after 11 a.m. Tuesday.Police say it's unclear whether the other person in the room is a teacher or staff member.Railsback says it's not known if the parent has a weapon. Hostage negotiators and the police department's SWAT team are at the scene, he says.The Riverside Unified School District said the campus was under lockdown due to a "disturbance inside of a classroom.""So far he has not been willing to come out," Railsback says about the man.All students have been safely evacuated, according to the school district.The Associated Press and CNN contributed.

RIVERSIDE, Calif. —

Authorities say a parent has barricaded himself in a Southern California elementary school classroom with at least one other person.